LONDON, April 13 (Reuters) - Aluminum hit a six-year high on Friday and remained on track for the biggest weekly gain on record after the United States imposed sanctions on Russia's UC Rusal, the world's second-biggest producer of the metal.

Traders have scrambled to stockpile aluminum this week, given concerns that the removal of Rusal metal from the market will further tighten availability.

"If you look at the scope of Rusal supply, they were a very cost-efficient supplier and a very substantial one, and they were well meshed into a lot of other manufacturers downstream," said Natixis analyst Cameron Karami.

"If Rusal supply does (largely) go out of the market; ie, if they can't continue to sell via a third party, that will lead to a meaningful deficit, and that is certainly still positive for prices."

On-warrant aluminum stocks in London Metal Exchange warehouses -- metal available to the market -- fell by nearly 100,000 tonnes, exchange data showed on Friday, almost the same quantity as added to headline stocks the previous day.

Traders say the aluminum delivered to LME warehouses this week was probably produced by Rusal and that the canceled warrants -- material earmarked for delivery and no longer available -- is likely to be from other companies.

* ALUMINIUM PRICES: London Metal Exchange aluminum hit its highest since March 2012 at $2,340 a tonne and was at $2,321.50 by 1020 GMT, down 0.2 percent. On course for a weekly gain of 14 percent, this would be the biggest one-week rise since the contract was launched in its current form in 1987, Reuters data shows.

* U.S. ALUMINIUM STOCKS: Almost all the aluminum in the United States was removed from Comex warehouses this week. Stocks tumbled by about 44,000 tonnes to 11,168 tonnes. <AL-TTLTTDY-STX>

* SPREADS: The rush for stocks was reflected in time spreads on the LME, with the premium on the cash aluminum contract rising to $56 a tonne over the three-month future <CMAL0-3>, its highest in at least a decade.

* COPPER: LME copper was up 0.6 percent at $6,862 a tonne after a 1.9 percent drop the previous session. The base metals broadly benefited from sharper appetite for cyclical assets on Friday, reflected by strength in equities.

* OTHER METALS: LME zinc was up 1.2 percent at $3,130 a tonne, while lead rose 0.4 percent to $2,342, tin advanced by 1 percent to $21,105 and nickel jumped by 2.3 percent to $14,035.

(Reporting by Jan Harvey Additional reporting by Pratima Desai in London and Melanie Burton in Melbourne Editing by David Goodman)